Pyrometer.



P. D..FO0TE & E. H. FISHER.

PYROMETEB. APPLICATION FILED JULY I6. I917.

1,283,717; Patented Nov. 5, 1918.

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wn'usssss UNITED STATES PATENT onnroa.

PAUL D. FOQTE ANI) EDWIN H. FISHER, OFPITTSBURGH, PENNSYLVANIA, A SSIGN'ORS TO SCIENTIFIC MATERIALS COMPANY, A CORPORATION OF PENNSYLVANIA.

PYROMETER.

Specification of Letters Patent.

Patented Nov. 5, 1918.

Application filed m 16, 1917. Serial No. 160,713.

- To all whom it may concern Be'it'known that we, PAUL D. Foo'rr. and

EDWIN H. Frsnnn, both residents of Pitts bur h, in the county of Allegheny and State of ennsylvania, have invented a new and useful Im rovement in Pyrometers, of which the ollowin is a specification.

This invention re ates to optical pyrometers.

Among the objects of the invention are the provision of means for: reducing the light beam caused; by incandescence of a heated object to the same intensity as a light beam froma constant source, the adjustable means for securing this condition being connected to and operating a d al, or scale, for indicating by the degree of ad ustment-required, the temperature of the meandescent object.

Another object is to bring the light ray derived from an object heated to incandescence to the same intensity as a light beam derived from a standard source of known intensity, by means ofa movable wedge of light-absorbing material in the path of the beam derived from incandescent objects, and means to project in juxtaposition. the images formed bythe respective li ht beams with a dividing line so that w en the two beams are reduced to the same intensity the dividing line between the 1mages will disappear.

Other objects and advantages will be more fully set forth in the followin specification.

Referring to the drawings, .igure 1 shows a front elevation of the pyrometer; Fig. 2

shows a vertical central longitudinal section In making such comparisons by ordinary means a great deal depends upon the personal quation, since one person may say that two lights are of the same intensity, or

two shades of color the same, whereas another person might under exactly the same conditions have a different opinion. The present invention is particularly intended to render the comparison of intensity of lights and shades of color more easy and more accurate, regardless of the personal equation, by eliminating in. part the necessity of making an actual comparison of color. This is done b forming the images produced by the two ights in juxtaposition, as for example into halves of a circle, and in such manner that so long as there is a difierence -of intensity in the lights forming the im-- ages, the dividing line or diameter between them will appear as a definite line. When 'this line disappears, so that the fields form a single und1vided circular image, the intensities will have been brought to the same degree, and this result will be accurate regardless of variation in the eyes of the ob servers. 2

Referring to the drawings,the pyrometer shell is preferably made of aluminum castings, comprising a circular casing 1, shown in Fig. 1, having an eye-piece barrel 2 suitably attached perpendicular to the face of the main casing, and anadjustable focusing objectivebarrel 3 attached to acasting 4:

adapted to close the main casing 1, as illus-' trated in Fig. 2. A supplementary barrel 5 is carried on the face 0 the casin 1, perpendicular to the common axis of barrels 2 and 3. The barrel 2 is fitted with an eyepiece 6, which carries a plane glass 7 of a suitable color, such as red, and a lens 8 of clear glass. The inner end of this barrel 2 has a restricted circular opening 9.

Just beyond this opening, inside the main casing 2, triangular prisms 10 and 11 are fastened together on their diagonal faces. A certain part of the diagonalface of the prism 11 is covered with silver, while the entire face of the prism 10, and the upper part of the prism 11, are clear, the border of the silver-covered portion being sharply cut parallel to the edges of the dlagonal face,

and extending horizontally across the face of the prism, this edge of the silvered portion being exactly in the axis of the barrels 2 and 3, which passes through'the center of the opening 9, as will be readily understood.

The supplementary barrel 5 is arranged so that its axis is perpendicular to the axis of the barrels-2 and 3 on the line separating the silvered and clear portions of the prism 10.

nesaviv In the barrel a source oi? li ht 12 is provided. This light may be 0% any desired form, and is standardized so as to give the exactintensity of light necessary for. the purposes more fully set forth below.

The barrel 3 has an outer lens 13, and at its inner end has a restricted central opening 1d axially alined with the opening 9 above described, so that light passing into the barrel 3 can pass through the openings 14; and 9 to theeye-piece 6 in a direct line, except as the lower part of it is cut oil by the silvered surface of the prism 10. Therefore light through the barrel 3 will form a semicircular image to the observer. Likewise light from the standardized source 12 will pass through 15 and ground glass 16, and fall upon the silvered portion of the prism 10, part of it being reflected by the lower silvered side thereof, through ing image of semicircle to the observer through eye-piece The semicircles referred to are supplementary, together making the complete circle, one half of the images forming the complete circle being derived from each of the respective sources. The colored glass 7 will cause the light from each source to take on the same color, and the appearances of the two images will difier according to the intensities only of the respective sources.

lilounted inside the main casing is a suitable frame 17, the edges of which are retained by a lower flange 18, and an upper flanged gear wheel 19, the gears of said wheel meshing with teeth on a rack formed at the upper side of the retaining frame 17. The middle portion of the frame is cut away, and mounted inside the frame is a wedge-shaped member 23,

. preferably of light-absorbing gelatin inclosed in glass. The gear wheel 19 is fixed on shaft 21, which has a knurled head 22, outside or": the main casing. By rotating this head, the frame 17 and its wedge are moved across the path of light passing through the barrel 8. As the thicker portion of the wedge intercepts more light, the intensity will decrease, and vice versa.

Consequently by this means light from the incandescent source may be reduced to any desired intensity, as to that of the standardized lamp 12.

fixed to the post 21 is a pointer 24, which eobperates with a circular scale 25 on the face of the main casing, and indicates the temperature being measured, as more fully described below.

The operation of the device is as follows: The source of light 12, and the scale 25, are standardized and calibrated by the instru ment maker, preferably so that the scale will indicate temperature directly. The observer trains the main barrel 3 upon the incandescent ob"ect the heat or which is to the opening 9, and formbe measured, at a proper distance therefrom. Light is conducted through the two alined barrels 2 and 3, and forms a semicircular image to the observer at the eye-piece v6.. The intensity of this image will vary with the heat of the object. The supplementary barrel 5 conveys light from the standardized source 12, and this light, reflected by the silvered surface of the prism 10, also forms a semicircular image, supplementary to that from the main barrel, at the eye piece. By the glass 7 these images are ren dered of the same color, and difier only in intensity. So ion as there is a difference in the intensity 0 the two lights, the two semicircles will appear to be separated by a sharp line, but when the wedge 23 is moved to change the thickness thereof sufficiently to make the intensity of the light from the heated object equal to that derived from the standardized source, the two images will merge, and the dividing line wilhdisappear, at which point the intensit of light derived from the two sources will be equal. The pointer 24-, which follows the movement of the wedge 23, will then read upon the scale 25, in terms of the temperature of the incandescent object being observed.

The many advantages of completeness of construction, simplicity of operation, and accuracy of observation incident to this invention will be apparent to those with the art.

We claim 1. An optical pyrometer comprising an form of adjacent images of the same color.

2. An optical pyrometer comprising an eyepiece, a casing containing a source oil light of constant intensity, 9. barrel adapted to receive light from an incandescent object the temperature of which is to be determined, means to vary the intensity light received from the incandescent object by a sliding wedge of light-absorbent material, and means to pass the two light beams to the eye-piece in the form of adjacent ages of the same color.

3. An optical pyrometer comprising an eye-piece, acasing containing a source ct light of constant ig nsity, a barrel adapted to receive light fro n incandescent object the temperature otwliich is to be measured,-

eye-piece inthe form of adjacent images of the same color.

4. An optical pyrometer comprising an eye-piece, a casing containing a fixed source of light of fixed intensity, a translucent diffusing screen illuminated by the fixed source of light, a barrel adapted to receive light from an incandescent object the temperature of which is to be measured, means to vary the intensity of light received from the incandescent object, and means to eliminate one half the light beam from each source and to pass the remainders of the two light beams to the eye-piece in the form of adjacent images of the same color.

5. An optical pyrometer comprising an eye-piece, acasing containing a source of light of constant intensity, a translucent diffusing screen illuminated by the light, a'

barrel adapted to receive light froman inczfiide'scent object the temperature ofwhich is to be measured, means tovar the intensity of light received from the incandescent object, and means to eliminate one half the light beam from each source and to pass the remainders of the two light beams to the eye-piece in the form of adjacent supplementary images of the same color.

6. An optical pyrometer comprising an eye-piece, a barrel containing a source of light of constant intensity, a barrel adapted to receive light from an incandescent object the temperatur e of which is to be measured, means to var the intensity of light received from the incandescent object comprising a translucent wedge, and means comprising a prism having part of its face covered with a reflecting opaque medium to pass the two light beams to the eye-piece in the form of adjacent supplementary images of the same color.

7. An optical pyrometer comprising an eye-piece, a barrel containing a source of light of constant intensity, a barrel adapted to receive light from an incandescent obj ect the temperature of which is to be measured, means comprising a translucent wedge to vary the intensity of light received from the incandescent object, and means comprising a reflecting element to eliminate one- -candescent object'the temperature of which is to be measured, means to vary the intensity of light received from the incandescent object, and means comprising a prism to pass the two light beams to the eye-piece in the form of adjacent supplementary images of the same color.

In testimony whereof, we'have hereunto set our hands. 7

PAUL D. FOOTE. EDWIN. H. FISHER. Witness: 7

GLENN H. LERESCEE. 

